The present invention relates to the art of biological indicator systems. It finds particular application in conjunction with indicating the completeness of a sterilization process and will be described with particular reference thereto.
Heretofore, various sterilization indicating systems have been provided. The systems generally included an element, e.g. a pad which was inoculated with a spore or other microorganism. The pad was mounted in a container and connected with the container exterior by a tortuous path. The container was disposed such that during a gas sterilization process, the pad was subject to substantially the same sterilizing conditions by gas that penetrates the tortuous path as the articles being sterilized. At the end of the sterilizing operation, the tortuous path was closed, a glass ampule containing a culture medium was fractured, and the pad and culture medium were brought together. After an appropriate incubation period, the culture medium was examined for evidence of growth of the inoculated microorganisms. A lack of microorganism growth was indicative of sterilization and growth of the microorganisms was indicative that the sterilization process was not complete. See for example U.S. Pat. Nos. 4,461,837 and 4,743,537.
One drawback of the prior art sterilization indicator systems was that they were limited to steam and gas sterilization processes. Liquids did not reliably penetrate the tortuous path or displace trapped air adjacent to the pad. Accordingly, they were unreliable as indicators of sterilization in a liquid sterilization process.
Another disadvantage of the prior art sterilization indicating systems was that they used a frangible glass ampule. The glass ampule was selected in order to withstand the internal pressure increase when the culture medium was heated to the temperature of sterilizing steam. However, the glass ampules had inherent drawbacks. For example, the glass acted as a heat sink, reducing the temperature to which an adjoining inoculated pad was subject. Also, glass ampules were subject to cracking at inappropriate times such as in transit or sudden changes in temperature. Yet, fracturing the glass ampule at the appropriate time was sometimes difficult.
The present invention provides a new and improved biological indicating system which is suitable for use in liquid sterilant systems, yet overcomes the above referenced problems.